kernel sentence核心句 later time后时性 lexical connector词汇纽带 exical meaning词汇意义 linear structure线性结构 linking verb连系动词 logical connector逻辑纽带 logical necessity逻辑必然 low-rise低升调K kernel sentence 核心句 L later time 后时性 lexical connector 词汇纽带 lexical meaning 词汇意义 linear structure 线性结构 linking verb 连系动词 logical connector 逻辑纽带 logical necessity 逻辑必然 low-rise 低升调